Electroerosive burr-removing method and apparatus



Feb. 20, 1968 L. MATTEUCCI 3,370,146

ELECTROEROSIVE BURR-REMOVING METHOD AND APPARATUS Filed March 9, 1964FIG.6.

INVENTOR LUIGI MATTEUCOI BYw I United States Patent Ofiice 3,370,146Patented Feb. 20, 1968 3,370,146 ELECTROEROSIVE BURR-REMOVING METHOD ANDAPPARATUS Luigi Matteucci, Porretta Terma, Provincia de Bologna, Italy,assignor to S.p.A. ()fiicine Meccaniche Fratelli Daldi & Matteucci,Milan, Italy, a company of Italy Continuation-impart of application Ser.No. 225,227, Sept. 2-1, 1962. This application Mar. 9, 1964, Ser. No.350,154

Claims priority, application Italy, June 19, 1962,

24,610, Patent 671,375 8 Claims. (Cl. 219-68) ABSTRACT OF THE DISCLOSUREApparatus for and a method of removing protruding irregularities, suchas burrs, from engaging gear surfaces, including means for rotatablymounting a first gear, means for rotatably mounting a second gear inmesh with the first gear and electrically insulated therefrom, means forrotating one of said gears and an electric circuit including said gearsin series for passing low voltage, high current electrical energybetween the gears intermittently without a dielectric therebetween incombination with means for determining the noise produced on rotation ofthe gears and the method of use of such apparatus whereby protrusions,such as burrs and the like on the engaging surfaces of the gears areburnt off to provide gears which are quiet when rotated in mesh.

This application in a continuation-in-part of now abandoned copendingapplication Ser. No. 225,227, filed Sept. 21, 1962.

In the manufacture of articles, such as gears, protruding irregularitiessuch as burrs are sometimes accidentally formed in the gear surfaces.These protruding irregularities are objectionable in that they producenoise on rotation of mating gears in mesh. In addition, protrudingirregularities in mating gear surfaces produce undesirable stressconcentrations which could result in serious damage to the gears.

In the past it has been the practice to position gears as they areproduced on noise level measuring apparatus on which the gears arerotated in mesh one with the other, or with a master gear, to measurethe noise produced by the meshed gears in operation. The level of thenoise in such tests is indicative of the protruding irregularities inthe surfaces of the gear teeth in contact. After protrudingirregularities have been found to exist by the noise measuring, minuteinspection of the gear to locate the actual defect therein has beenrequired in the past.

A separate inspection is then required to remove the discovered defect,after which a recheck of the noise level of operation of the gear isnecessary to insure that all of the defects have been dicsovered andremoved. This procedure 'is obviously time consuming and not in keepingwith modern mass production techniques.

It is therefore one of the objects of the present invention to provideimproved apparatus for removing protruding surface irregularities fromgears or the like.

Another object is to provide an improved method of removing protrudingsurface irregularities from gears or the like.

Another object is to provide apparatu for simultaneously checking thenoise level of gears rotated in mesh and removing protruding surfaceirregularities from the gears.

Another object is to provide a method for simultaneously checking thenoise level of gears rotated in mesh and removing protruding surfaceirregularities from the gears.

Another object is to provide apparatus for removing protrudingirregularities, such as burrs, from the teeth surfaces of gears rotatedin mesh the one with the other, or with a master gear, includinginsulated spindle structure for rotating a first gear in mesh with asecond gear, means for mounting the second gear in mesh with the firstone and for rotating them, also means for intermittently passing anelectric signal of low voltage and high current between the two gears inmesh.

Another object is to provide a method of removing protrudingirregularities from a work gear comprising rotating a gear or a mastergear having no irregularities in the surface and rotating a gear havingprotruding irregularities in the surface meshing with the other gear,measuring the noise level of the rotating meshed gears andintermittently passing an electric signal of low voltage and highcurrent between the two gears until the noise level of the rotatingmeshed gears is reduced below a predetermined maximum value.

Another object is to provide apparatus for and a method of electricallyremoving irregularities from the surfaces of gears or the like which aresimple, economical and efiicient.

Other objects and features of the invention will become apparent as thedescription proceeds, especially when taken in conjunction with theaccompanying drawings, illustrating a preferred embodiment of theinvention, wherein:

FIGURE 1 is a partly diagrammatic and partly schematic illustration ofapparatus for electrically removing gear surface irregularities inaccordance with the method of the invention.

FIGURE 2 is an enlarged section view of a portion of the apparatusillustrated in FIGURE 1 taken substantially on the line 2-2 in FIGURE 1.

FIGURE 3 is a further enlarged section view' of a portion of FIGURE'Zillustrating the gear teeth of FIG- URE 2 in line contact.

FIGURE 4 is a section view of the gear teeth illustrated in FIGURE 3taken substantially on the line 44 in FIGURE 3.

FIGURE 5 is a section view of the gear teeth illustrated in FIGURE 3with the gears rotated slightly relative to each other from theirposition in FIGURE 3 to illustrate that point contact is providedbetween the gear teeth when a burr is present therebetween.

FIGURE 6 is a section view of the gear teeth illustrated in FIGURE 5taken substantially on the line 66 in FIGURE 5.

With particular reference to the figures of the drawing, one embodimentof the present invention will now be considered in detail.

As shown best in FIGURE 1, the apparatus 10 for removing protrudingirregularities, such as burr 1-2 from the surface of a work gear 20comprises a portion of the apparatus 14 for measuring the noise level ofgears rotated in mesh including structure 22 for rotatably mounting agear 24 in mesh with gear 20 and insulated structure 26 for rotatablymounting the gear 20 in mesh with the gear 24. Apparatus 10 furtherincludes the electric circuit 28 for applying an electric signal of lowvoltage and high current between gear 20 and gear 24.

In operation, as gear 20 and gear 24 are rotated in mesh on the noiselevel measuring instrument 14, the gears 20 and 24 will have a linecontact as long as no protruding irregularities exist in the gearsurfaces so that current passing therebetween will be spread over arelatively large area. Where a protruding irregularity, such as burr 12,appears on the surface of the gears, the current passing between the twogears will be concentrated in the iirregularity due to the point contactbetween gears 21 and 24, so that the irregularity will be burned off.

The two gears are rotated in mesh until the protruding irregularitieshave been removed from the gears so that the noiselevel of the rotatingpair of gears is below a predetermined maximum as measured by theapparatus 14.

The noise level measuring apparatus 14 is well known in the gearchecking art and will therefore not be considered in detail hereinexcept for the structures 22 and '26 which also form a part of theprotruding irregularity removing apparatus 10.

More specifically the structure 22 for mounting the gear 24 for rotationcomprises the rotatable spindle sup ported for rotation in the frame 16of the apparatus 14 and the shaft 32 secured in the spindle 30 forrotation therewith. Shaft 32 has the reduced diameter portion 34 onwhich the gear 24 is mounted as by convenient key means (not shown) forrotation with the shaft 32.

The nut and pressure washer 42 are provided on shaft 32 for removablysecuring the gear 24 on the shaft 32.

The work holding member 36 for rotatably supporting the end 38 of theshaft 32 during rotation of the spindle 30 also supported in frame 16 ofapparatus 14 completes the structure 22 for rotatably mounting the gear24.

T he structure 26 for mounting gear 20 in mesh with gear 24 includes therotatable spindle 46, the end 48 of which is electrically insulated fromthe frame 16 of the noise testing apparatus 14 by the insulating pad 54.The end portion 48 of spindle 46 securely receives the shaft 56 wherebythe shaft 56 is caused to rotate with the spindle 46. The shaft 56 isprovided with the reduced diameter portion 60 on which the gear 20 issecured for rotation with the shaft 56 as by convenient key means (notshown) in conjunction with the clamping washer 62 and the nut 64.

The work holding member 66 is adapted to rotatably support the end 68ofthe shaft 56. The work holding member 66 is in turn supported by theframe 16 of apparatus 14 and is insulated therefrom by the pad ofinsulating material 72. Thus it will be seen that except for the gear 20in mesh with the gear 24, the shaft 56 and end 48 of spindle 46 areelectrically insulated from the frame 16 of apparatus 14.

The circuit 28 for applying an electrical signal of low voltage and highcurrent between the gear 20 and gear 24 in mesh includes the collectorring 74 secured to the end portion 48 of the spindle 46. The contactshoe 76 is resiliently biased in the chamber 78 formed in bracket 80into contact with the collector ring 74 by the spring means 82. The shoe76 is guided in its reciprocal movement on the rod 84 secured within thechamber 78.

The electrical conductor 86 is secured to the contact shoe 76 through anopening 88 in the bracket 84 The frame 16 of the noise testing apparatus14 is connected to a second electrical conductor 90 by convenient means,such as bracket 92. Conductor 90 is therefore effectively electricallyconnected through the frame 16 of the noise testing apparatus 14 and theshaft 32 to the gear 24 while the conductor 86 is effectivelyelectrically connected through the contact shoe 76, portion 48 ofspindle 46 and shaft 56 to a gear 26 mounted on the shaft 56.

At the other ends the conductors 86 and 94 are secured to the oppositeends of the secondary winding 94 of transformer 96. Transformer 96 alsoincludes the primary winding 98 having multiple taps 101 The primarywinding 98 of transformer 96 through multiple tap 100 is capable oftapping different selected voltages from the conductors 102 and 104which are connected to an alternating source 51) of low voltage and highcurrent through the double pole, single throw switch 166.

The taps 100 and selector switch 108 in conductor 110 permit varying ofthe voltage in the secondary coil 94 of transformer 96 between, forexample three and onehalf and five volts. Transformer 96 is a step-downpower transformer of, for example, seven hundred fifty watt capacity.Thus at between two and five volts between three hundred seventy-fiveand one hundred fifty amperes of current may flow in the conductors 86and 90.

The transformer 96 is energized on closing of the switch 106. Switch 106is closed on energizing the solenoid 112 by completing the circuitthrough the secondary winding 114 of transformer 116 by pressing thepush-button switch 118. The primary winding 52 of transformer 116 isconnected to the source of power 50 through the conductors 162 and 104.The circuit for energizing the switch 106 is provided as a safetymeasure. Thus the transformer 116 is a step-down transformer and thecurrent passing through the switch 118 is only sufficient to actuate theswitch 106.

In over-all operation it is desired to measure the noise level of a gear20 rotated in mesh with a gear 24 and to simultaneously remove pr udingirregularities, such as the burr 12, from the surfaces of the gear whichare in contact with the surfaces of the gear 24. The gear 20 istherefore first mounted on the shaft 56 in mesh with the gear 24, asshown in FIGURE 1. The gears 20 and 24 are then rotated in mesh onrotation of the spindle 30 or spindle 46 or both.

During rotation of the gear 20 and the gear 24 considerable noise whichmay be measured by the noise measuring apparatus 14 is produced ifprotruding irregularities are present on gears.

The teeth of the gears during rotation of the gears in mesh are inmoving line contact, as illustrated in FIG- URE 2, when no protrudingirregularities exist therebetween. However, when a burr is present onsurface 120 of work gear 20, as illustrated in FIGURE 5, the linecontact illustrated in FIGURES 3 and 4 is reduced to a point contact, asillustrated in FIGURES 5 and 6.

Thus on noting that the noise level of the gears in mesh is above apredetermined maximum an operator of the apparatus 10 presses thepush-button 118 for a period of for example two to five seconds to closethe switch 106 and energize the transformer 96 whereby a low voltage offor example two to five volts and a high current is passed between thegears during rotation thereof. The line contact provided by the gearteeth, as illustrated in FIG- URES 3 and 4, provides a sufi'lcient pathfor the high current to prevent overheating of the gear teeth at theirmoving line contact at the usual speed of the sound level measuringapparatus 14. However, when a point contact occurs as at burr 12, theconcentration of current at a single point is so great that the burr isheated to the point that it is completely burned away.

The rotating speed of the gears 20 and 24 must be such that a superheating of the teeth surfaces is prevented along the moving line contactbetween the gears. The usual speeds of between five hundred and twothousand revolutions per minute at which sound level measuring apparatus14 is operated are sufficient for this purpose.

The removal of the burr as it is best understood is a complete burningof the metal forming the burr and does not appear to be particularlyeffected by the pressure between the gears.

The signal applied between gear 20 and gear 24 has been indicated asbeing an alternating signal. It is understood that a unidirectionalsignal should work equally as well as an alternating signal.

The burr removing operation is intermittent. That is to say that onnoting a noise level higher than a maximum desired level the operatorpresses the push-button 1 18 for three or four seconds during which thework gear may make a series of revolutions and complete a deburringoperation. The noise level is then again checked and the deburringoperation is repeated if necessary. Usually one, three or four secondperiod is sufiicient to remove burrs.

If noise is produced in the meshed gears by factors other thanprotruding irregularities on the gear teeth the completion of thedeburring operation may be visually recognized by the disappearing ofthe characteristic sparking or arcing which may be observed between theteeth of the gears as soon as the push-button is operated.

While one embodiment of the present invention has been disclosed indetail other embodiments and modifications of the invention arecontemplated. Thus the invention may be modified to permit removing ofprotruding irregularities from the contacting teeth of straight spur,helical spur, straight bevel and helical bevel gears as well as fromteeth having an involute profile. It is the intention to include allsuch modifications and embodiments as are defined by the appended claimswithin the scope of the invention.

What I claim as my invention is:

1. Apparatus for removing protruding irregularities from the surfaces ofa pair of gears to insure quiet operation thereof, comprising means fordetermining the noise produced by the gears rotating in mesh, means forrotating the gears in mesh on the means for determining the noise andmeans for intermittently passing an electric signal of low voltage andhigh current between the gears rotating in mesh on the means fordetermining the noise for periods of between two and five seconds tosimultaneously remove protruding irregularities from the gears andreduce the noise produced by the gears rotating in mesh.

2. Structure as set forth in claim 1 wherein the voltage of the electricsignal is between two and five volts.

3. Structure as set forth in claim 1 wherein the current of the electricsignal is between one hundred fifty and three hundred seventy-fiveamperes.

4. Structure as set forth in claim 1 wherein the gears are rotated inmesh at between five hundred and two thousand revolutions per minute.

5. The method of removing protruding irregularities from the surface ofa pair of gears to insure quiet operation thereof, comprisingdetermining the noise produced by the gears rotating in mesh, rotatingthe gears in mesh on the means for determining the noise andintermittently passing an electric signal of low voltage and highcurrent between the gears rotating in mesh for periods of between twoand five seconds to simultaneously remove protruding irregularities fromthe gears and reduce the noise produced by the gears rotating in mesh.

6. The method as set forth in claim 5 wherein the voltage of theelectric signal is between two and five volts.

7. The method as set forth in claim 5 wherein the current of theelectric signal is between one hundred fifty and three hundredseventy-five amperes.

8. The method as set forth in claim 5 wherein the gears are rotated inmesh at between five hundred and two thousand revolutions per minute.

References Cited UNITED STATES PATENTS 1,668,840 5/1928 lDomizi 51-261,917,178 7/1933 Wolfe .L. 51-46 2,393,113 1/1946 Lucas 73-462 2,526,42310/1950 Rudorif 219 69 2,899,535 8/1959 Kra-ll 219 -69 2,974,215 3/1961Inoue 219-69 FOREIGN PATENTS 1,224,109 2/1960 France.

RICHARD M. WOOD, Primary Examiner.

R. F. STAU'BLY, Assistant Examiner.

